Patent GB-712398-A (GB)
Title: A method of treating black grease
Inventor: KIRBY JOSEPH HERMAN
IPC: C11C3/04
Filed: 1951-01-15
Abstract: A method of treating black grease, the product obtained on acidulation of the soap stock from alkali refining of glyceride oils and fats, comprises slowly heating the black grease to avoid foaming, over a period of at least one hour to a minimum temperature of 300 DEG  F. at which temperature rapid esterification of di-glycerides and other esterifiable substances of black grease commences, maintaining the temperature at said minimum temperature at 300 DEG F. or above for at least one hour to effect substantially complete esterification and simultaneously removing water in the form of vapour.  The process may be carried out under superatmospheric pressure or under vacuum and in the presence of hydrogen or another inert gas such as nitrogen or carbon dioxide and an esterification catalyst may be used.  The reaction product may be hydrogenated, e.g. using a finely-divided nickel catalyst, usually with diatomaceous earth in a carrier of oil.  In examples: black grease, containing fatty acids obtained on acidulation with sulphuric acid of soap stock from the caustic soda refining of soya bean oil, is heated under pressure with hydrogen, steam and hydrogen being blown off intermittently until all the water present or formed is evaporated. The product is then hydrogenated using a catalyst consisting of diatomaceous earth, finely-divided nickel and a glyceride oil.  A further small amount of esterification takes place during the hydrogenation. The product is then filtered and refined (1) and (2); a cotton seed oil black grease obtained in a similar manner to the starting material in (1) is gradually heated in a pressure vessel under hydrogen whilst a mixture of steam and hydrogen is bled off continuously and vented hydrogen is replaced with fresh hydrogen. The product is hydrogenated using a nickel catalyst consisting of both fresh and spent catalyst used in the hydrogenation of refined cotton seed oil (3).  The product is filtered and is usually refined as is customary for glyceride oils, a bleaching step before or after hydrogenation being desirable.  The product may be used without hydrogenation and may be separated to give an oil and a fatty acid fraction.  The black grease is converted by the esterification to a product of lower viscosity which does not emulsify or foam and contains sterols and an increased amount of triglyceride oil.  The hydrogenation product contains free fatty acids, glyceride oils, free and esterified sterols, other esters and unsaponifiable material and may be split to obtain fatty acids useful as promoters in the polymerization of unsaturated compounds in synthetic rubber production and for making metallic soaps, e.g. of aluminium, lithium and calcium for use as greases.  The fatty acids may be employed as a substitute for stearic acid.  The hydrogenated product may be further esterified with glycerine on another polyhydric alcohol.  The black grease may be purified prior to treatment, e.g. proteins may be removed and the material may be bleached, e.g. with sodium hypochlorite, perborate, persulphate or chlorite.  The bleaching is preferably carried out after hydrogenation.  In addition to, or alternatively to the purification, the black grease or the hydrogenated products or both may be treated with phosphoric and citric acids.  Spent catalyst from the hydrogenation of the purified oil and waste hydrogen from hydrogenation apparatus may be used. Black grease derived from soap stock from other oils than soya and cotton seed oils may be employed and may be of animal or vegetable nature such as fish oils, drying oils and non-drying oils.